| 1. |
- Ahlgren, Joakim, et al.
(författare)
-
Orsaker till minskande syrehalter i Bottenhavet
- 2017
-
Rapport (refereegranskat)abstract
- Resultat från den nationella miljöövervakningen visar att syrehalterna i Bottenhavet har minskat sedan 1970-talet, en minskning som accelererat från 1990. För att ha möjlighet att på något sätt kunna åtgärda denna försämring av den marina miljön är det nödvändigt att identifiera orsakerna till denna syreminskning, eftersom olika orsaker kan kräva olika former av åtgärder. Om orsaken till exempel är ökad syreförbrukning beroende på regional övergödning, skulle detta innebära ökat behov av regionala reningsåtgärder. Målsättningen med projektet var därmed att ge en tillförlitlig förklaring till de sjunkande syrehalterna i Bottenhavet under de senaste 20 åren genom att använda data från de nationella miljöövervakningsprogrammen. De huvudhypoteser som undersöktes som orsaker till de sjunkande syrehalterna var: • Ökad regional gödning av Bottenhavet och därmed ökad produktion. • Tillförsel av syrefattigt och fosfatrikt från Egentliga Östersjön. • Starkare haloklin och försämrad ventilation av Bottenhavets djupvatten. • Ökad temperatur och ökad tillförsel av löst organiskt kol. Analys av tidsserier och modellanalyser utifrån miljöövervaknings- och forskningsdata visade att den observerade syrehaltsminskningen i Bottenhavets djupvatten främst beror på en ökning av vattentemperaturen och delvis på en ökning av löst organiskt kol i vattnet, samt tillflöde från Egentliga Östersjön. Dataanalysen visade däremot inget tydligt stöd för att ökad produktion av biomassa i Bottenhavet orsakat de minskande syrehalterna. Detta gäller indikatorer för växtplankton, sedimentation och bakterieplankton som alla förväntas öka vid ökad produktion och det finns således inga direkta indicier för att stödja hypotesen om ökad gödning av Bottenhavet. Sammantaget visar de analyser som gjorts inom projektet att Bottenhavets framtida hälsa främst gynnas av en kombination av åtgärder för att motverka globala klimatförändringar, samt åtgärder för att förbättra vattenkvaliteten i Egentliga Östersjön. Näringstillförsel från Bottenhavets avrinningsområden bedöms främst ha haft betydelse för syresituationen i kustnära vattenförekomster. Den bedöms därför inte i betydande omfattning ha orsakat de minskande syrehalterna i Bottenhavets utsjöområden.
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| 2. |
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| 3. |
- Andersson, Agneta, et al.
(författare)
-
Strategi för kontrollerande övervakning av Bottenhavets vattendistrikt
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Ett pelagialprogram har tagits fram för övervakning i relativt opåverkade referensområden i kustvattentyperna 16 t.o.m.19 i Bottemhavet. Programmet bör kunna ligga till grund för uppföljning av internationella, nationella och regionala miljömål samt följa upp ekologisk status. Den rumsliga variationen samt mellanårsvariationen hos pelagiala variabler i Bottenhavsområdet har använts som utgångspunkt för att beräkna provtagningsbehovet. Det föreslagna programmet innebär att mellan 48 och 60 provtagningar årsperiod, varefter ekologisk status kan bedömas. Designen gör det möjligt att med 80 % säkerhet bedöma ekologisk status med mätdata som ligger minst 20 % från klassgränserna. Mätprogrammet är designat för provtagningar -årsperiod. Stationer har slumpats ut i de olika typerna, och förslag på årliga provtagningslokaler anges i rapporten. Eftersom djupet vid de olika stationerna varierar, bör de flesta pelagiala variablerna provtas vid ett diskret djup i övre delen av vattenmassan, t.ex. 1 m djup. Av vetenskapliga och ekonomiska skäl är det viktigt att pelagialprogrammet samordnas för hela Bottenhavet.För mjukbottenfauna bedöms det befintliga integrerade programmet för trendanalys i Bottenhavet kunna tillgodose Vattendirektivets behov för kontrollerande övervakning i distriktet. Detta under förutsättning att Sundsvallsbuktens program fortsätter och att de nya nationella och regionala provtagningsområdena i södra Bottenhavet (Gräsö) etableras och drivs. Dimensioneringen av nuvarande nationellt och regionalt bottenfaunaprogram och områdesövervakning men har även visat sig vara väl anpassat för bedömningar inom ramen för Vattendirektivet. Enligt bedömningsgrunden bör minst 5 stationer användas för klassning av ekologisk status. Dessa stationer måste dock inte ligga inom samma vattenförekomst, utan kan vara lokaliserade i angränsande vattenförekomster. Den ekologiska statusen för mjukbottenfauna i enskilda vattenförekomster klassas genom extrapolering med hjälp av data från närbelägna områden med liknande bottenmiljö och påverkansgrad.Befintlig fiskebeståndsövervakning föreslås fortlöpa för att möjliggöra uppföljning av förändringar. En utökning av antalet övervakningsområden föreslås dock för att upprätta minst ett referensområde per inre och yttre kustvattentyp. En kombination av stratifierad och slumpmässig övervakning av fiskebestånden enligt nuvarande strategi föreslås, där djupintervallen stratifieras medan stationerna slumpas ut i respektive djupintervall.Provfiske och provtagning för miljögiftsanalys av fisk bör samordnas till samma provtagningstillfälle. Vidare bör den modell för samfinansiering och samordning som idag tillämpas av kustlänen i Bottniska viken för övervakning av fiskbestånd, samt och miljögiftsövervakning av fisk, fortlöpa även framöver.De ämnen som ingår i det pågående nationella programmet för miljögifter i fisk bör mätas även i de nya föreslagna områdena. När EU:s dotterdirektiv för prioriterade ämnen är beslutat och Vattenmyndigheterna fastställt miljökvalitetsnormer för särskilda förorenande ämnen, bör en översyn göras och ytterligare ämnen som är aktuella för Bottenhavet införlivas i övervakningsprogrammet. Miljögiftsövervakning i fisk bedöms kunna mätas med ett maximalt avstånd på 75 km mellan stationsområdena. Bedömning och extrapolera mätvärdena.För samtliga delprogram har en grova uppskattningar av kostnader för genomförandet gjorts.
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| 4. |
- Andersson, Agneta, et al.
(författare)
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Succession and growth limitation of phytoplankton in the Gulf of Bothnia (Baltic Sea)
- 1996
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Ingår i: Marine Biology. - 0025-3162 .- 1432-1793. ; 126:4, s. 791-801
-
Tidskriftsartikel (refereegranskat)abstract
- A one year field study of four stations in the Gulf of Bothnia during 1991 showed that the biomass was ca. two times, and primary productivity ca, four times, lower in the north (Bothnian Bay) than in the south (Bothnian Sea) during the summer. Nutrient addition experiments indicated phosphorus limitation of phytoplankton in the Bothnian Bay and the coastal areas in the northern Bothnian Sea, but nitrogen limitation in the open Bothnian Sea. A positive correlation between the phosphate concentration and the production/biomass ratio of phytoplankton was demonstrated, which partly explained the differences in the specific growth rate of the phytoplankton during the summer. Differences in photosynthetic active radiation between the stations also showed a covariation with the primary productivity. The relative importance of nutrient or light limitation for photosynthetic carbon fixation could not, however, be conclusively determined from this study. Marked differences in phytoplankton species composition from north to south were also observed. The number of dominating species was higher in the Bothnian Sea than in the Bothnian Bay. The distribution of some species could be explained as due to nutrient availability (e.g. Nodularia spumigena, Aphanizomenon sp.), while salinity probably limits the distribution of some limnic as well as marine species. The potentially toxic phytoplankton N. spumigena, Dinophysis acuminata and Chrysochromulina spp. were common in the Bothnian Sea but not in the Bothnian Bay. The pico- and nanoplankton biomass during late summer was higher than previously reported due to a revised carbon/volume ratio.
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| 5. |
- Bertilsson, Stefan, et al.
(författare)
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Photochemically induced changes in bioavailable carbon and nitrogen pools in a boreal watershed
- 1999
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Ingår i: Aquatic Microbial Ecology. - Oldendorf : Inter-Research. - 0948-3055 .- 1616-1564. ; 19:1, s. 47-56
-
Tidskriftsartikel (refereegranskat)abstract
- In several recent studies, a net stimulation of bacterial growth has been demonstrated after exposing humic surface waters to solar radiation or artificial ultraviolet radiation. This stimulation has been attributed to a photochemical release of bioavailable carbon or nitrogen compounds (ammonium). In a synoptic experiment, we exposed 0.2 mu m filtered water from 12 different habitats in a river system, dominated by allochthonous carbon input, to mild artificial UV radiation. A significant photochemical release of carboxylic acids of low molecular weight occurred. Furthermore, the exposure increased carbon-limited bacterial yield on average by a factor of 1.7. No photochemical production of free ammonium could be detected, which was in accordance with the lack of effects of radiation on bacterial growth yield under nitrogen-limited conditions. We conclude that, in boreal systems dominated by allochthonous carbon input, photochemical production of bioavailable carbon rather than nitrogen compounds is likely to positively influence the total substrate pool available for bacterial utilization.
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| 6. |
- Blackburn, Nicholas, et al.
(författare)
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Rapid determination of bacterial abundance, biovolume, morphology, and growth by neural network-based image analysis
- 1998
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 64:9, s. 3246-3255
-
Tidskriftsartikel (refereegranskat)abstract
- Annual bacterial plankton dynamics at several depths and locations in the Baltic Sea were studied by image analysis. Individual bacteria were classified by using an artificial neural network which also effectively identified nonbacterial objects, Cell counts and frequencies of dividing cells were determined, and the data obtained agreed well with visual observations and previously published values. Cell volumes were measured accurately by comparison with bead standards. The survey included 690 images from a total of 138 samples. Each image contained approximately 200 bacteria. The images were analyzed automatically at a rate of 100 images per h, Bacterial abundance exhibited coherent patterns with time and depth, and there were distinct subsurface peaks in the summer months. Four distinct morphological classes were resolved by the image analyzer, and the dynamics of each could be visualized. The bacterial growth rates estimated from frequencies of dividing cells were different from the bacterial growth rates estimated by the thymidine incorporation method. With minor modifications, the image analysis technique described here can be used to analyze other planktonic classes.
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| 7. |
- Båmstedt, Ulf, 1946-, et al.
(författare)
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Mixing depth and allochthonous dissolved organic carbon: controlling factors of coastal trophic balance
- 2016
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Ingår i: Marine Ecology Progress Series. - Oldendorf/Luhe : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 561, s. 17-29
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: The interacting effects of different mixing depths and increased allochthonous dissolved organic carbon (DOC) on the ratio of heterotrophic to autotrophic production (i.e. trophic balance) was evaluated in a mesocosm study with a stratified water column. An autumn plankton community from the northern Bothnian Sea showed significantly decreased phytoplankton production and somewhat increased bacterial production with added DOC. In addition, increased mixing depth further reduced phytoplankton production. With a deep pycnocline and added DOC, the system became net-heterotrophic, with an average bacteria-to-phytoplankton production ratio of 1.24. With a deep pycnocline without added DOC, the trophic balance was changed to 0.44 (i.e. autotrophic). With a shallow pycnocline, the system remained net-autotrophic irrespective of DOC addition. We propose that increased precipitation in northern Europe due to climate change may result in changed density stratification and increased allochthonous DOC transport to the sea, leading to more heterotrophic coastal aquatic ecosystems. Such a scenario may entail reduced biological production at higher trophic levels and enhanced CO2 emission to the atmosphere.
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| 8. |
- COCHLAN, William P, et al.
(författare)
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SPATIAL-DISTRIBUTION OF VIRUSES, BACTERIA AND CHLOROPHYLL-A IN NERITIC, OCEANIC AND ESTUARINE ENVIRONMENTS
- 1993
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Ingår i: Marine Ecology Progress Series. - Oldendorf : Inter-Research. - 0171-8630 .- 1616-1599. ; 92:1-2, s. 77-87
-
Tidskriftsartikel (refereegranskat)abstract
- The spatial distribution of viruses was investigated in the coastal and oceanic waters of the Southern California Bight, USA, and the brackish waters of the Gulf of Bothnia, Sweden, using the direct harvesting technique and transmission electron microscopy. The vertical and horizontal distributions of viruses were examined in relation to bacterial abundance and chlorophyll a. Total virus abundances ranged from 0.3 to 52 X 10(9) l-1; higher concentrations of viruses were found in the upper 50 m of the water column and in coastal environments. Viruses with capsid diameters less than 60 nm dominated the virus community, were morphologically characterized as bacteriophages and were responsible for most of the observed spatial variability. Bacteria abundance alone explained 67 % of the spatial variability in virus numbers, thereby suggesting that bacteria constituted the major host organisms for viruses in these physically diverse habitats.
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| 9. |
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| 10. |
- Huseby, Siv, et al.
(författare)
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Bacterioplankton growth
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Bacterioplankton growth rate is an indicator of the decomposition of organic matter and thereby trophic status of the Sea. The bacterioplankton metabolism accounts for about half of the mineralization of organic matter and thereby pelagic oxygen consumption.The bacterioplankton growth rate in deep waters indicates good trophic status in the off-shore Bothnian Bay and Bothnian Sea. Deep water growth rates were 67 % higher than at corresponding depths in the Atlantic Ocean, lacking excess enrichment. The decline that has earlier been reported has now ceased. During the last few years the growth rates has increased some and there is now no significant trends in any of the studied basins.
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| 11. |
- Jürgens, Klaus, et al.
(författare)
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[Indirect parameters: Ecosystem] Microbial community and processes
- 2021
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Ingår i: Climate change in the baltic sea. - Helsinki : Helsinki Commission (HELCOM). ; , s. 39-39
-
Bokkapitel (refereegranskat)abstract
- This overview focuses on bacterioplankton, comprising single-celled prokaryotes, i.e.,small organisms that lack a nucleus (Bacteriaand Archaea), in the water column, consuming organic carbon as an energy and carbonsource. Benthic prokaryotes and protozoa (i.e., unicellular zooplankton and zoobenthos) are also important but not included here. Bacteria are the major transformers of carbon, nitrogen, sulphur, and trace metalcycles in aquatic environments. The supply of organic carbon mainly controls bacterial biomass production. The bacterial community composition changes along the salinity andoxygen gradients of the Baltic Sea. Shifts in, e.g., food sources, temperature, and oxygen concentration result in rapid bacterioplankton community changes, with potential impact also on overall ecosystem functions, such as respiration, carbon consumption, and biomass production.
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| 12. |
- Kisand, Veljo, et al.
(författare)
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Combining culture-dependent and -independent methodologies for estimation of richness of estuarine bacterioplankton consuming riverine dissolved organic matter
- 2003
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 69:6, s. 3607-3616
-
Tidskriftsartikel (refereegranskat)abstract
- Three different methods for analyzing natural microbial community diversity were combined to maximize an estimate of the richness of bacterioplankton catabolizing riverine dissolved organic matter (RDOM). We also evaluated the ability of culture-dependent quantitative DNA-DNA hybridization, a 16S rRNA gene clone library, and denaturing gradient gel electrophoresis (DGGE) to detect bacterial taxa in the same sample. Forty-two different cultivatable strains were isolated from rich and poor solid media. In addition, 50 unique clones were obtained by cloning of the bacterial 16S rDNA gene amplified by PCR from the community DNA into an Escherichia coli vector. Twenty-three unique bands were sequenced from 12 DGGE profiles, excluding a composite fuzzy band of the Cytophaga-Flavobacterium group. The different methods gave similar distributions of taxa at the genus level and higher. However, the match at the species level among the methods was poor, and only one species was identified by all three methods. Consequently, all three methods identified unique subsets of bacterial species, amounting to a total richness of 97 operational taxonomic units in the experimental system. The confidence in the results was, however, dependent on the current precision of the phylogenetic determination and definition of the species. Bacterial consumers of RDOM in the studied estuary were primarily both cultivatable and uncultivable taxa of the Cytophaga-Flavobacterium group, a concordant result among the methods applied. Culture-independent methods also suggested several not-yet-cultivated beta-proteobacteria to be RDOM consumers.
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| 13. |
- Kisand, Veljo, et al.
(författare)
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Limited resolution of 16S rDNA DGGE caused by melting properties and closely related DNA sequences
- 2003
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Ingår i: Journal of Microbiological Methods. - 0167-7012 .- 1872-8359. ; 54:2, s. 183-191
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Tidskriftsartikel (refereegranskat)abstract
- The phylogenetic affiliation of 91 operational taxonomic units, randomly sampled from three aquatic microcosm experiments, was investigated by two PCR based and one culture dependent method. The occurrence of multiple melting domains and poor coupling between Tin and DGGE retardation was demonstrated to cause poor resolution at the species level in PCR-DGGE analysis of microbial communities. We also showed that the problem of multiple melting domains was particularly prone for brackish water bacterioplankton in the Flavobacterium genus, providing characteristic band morphology for this genus. Banding patterns from DGGE analysis may therefore be misinterpreted in terms of the species richness in natural bacterial communities, when using commonly applied universal primers. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 14. |
- Kisand, Veljo, et al.
(författare)
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Phylogeny of culturable estuarine bacteria catabolizing riverine organic matter in the northern Baltic Sea
- 2002
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Ingår i: Applied and Environmental Microbiology. - : American Society of Microbiology. - 0099-2240 .- 1098-5336. ; 68:1, s. 379-388
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Tidskriftsartikel (refereegranskat)abstract
- The objective of our study was to isolate and determine the phylogenetic affiliation of culturable estuarine bacteria capable of catabolizing riverine dissolved organic matter (RDOM) under laboratory conditions. Additions of RDOM consistently promoted the growth of estuarine bacteria in carbon-limited dilution cultures, with seasonal variation in growth rates and yields. At least 42 different taxa were culturable on solid agar media and, according to quantitative DNA-DNA hybridizations, constituted 32 to 89% of the total bacterial number in the enriched treatments. Five species in the Cytophaga-Flexibacter-Bacteroides group and one in the gamma-proteobacteria phylogenetic group (Marinomonas sp.) were numerically dominant during the stationary phase of the RDOM-enriched dilution cultures but not in the control cultures. Four of the isolates in Cytophaga-Flexibacter-Bacteroides group were putatively affiliated with the genus Flavobacterium. All dominating isolates were determined to be new species based on comparison to the current databases. The same group of species dominated independently of the season investigated, suggesting a low diversity of bacteria catabolizing RDOM in the estuary. It also suggested a broad tolerance of the dominating species to seasonal variation in hydrography, chemistry, and competition with other species. Taken together, our results suggest that a limited group of bacteria, mainly in the Flavobacterium genus, played an important role in introducing new energy and carbon to the marine system in the northern Baltic Sea.
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| 15. |
- Kuparinen, Jorma, et al.
(författare)
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Food web structure and function in the Gulf of Bothnia, the Baltic Sea
- 1996
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Ingår i: Ambio. - Stockholm : Swedish Royal Academy of Sciences. - 0044-7447 .- 1654-7209. ; , s. 13-21
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Tidskriftsartikel (refereegranskat)abstract
- To improve the spatio-temporal information of ecological variables, a multidisciplinary joint study between Finnish and Swedish marine scientists was conducted in the Gulf of Bothnia, 1991. The study corroborated previous reports, suggesting a markedly lower phytoplankton production and biomass of benthic fauna in the Bothnian Bay than in the Bothnian Sea, However, contrary to the general view, the offshore carbon fixation in the Bothnian Sea exceeded that at the corresponding coastal station. The results further indicated a greater importance of bacterioplankton production to the food web in the Bothnian Bay than previously assumed. The total carbon requirement of bacteria and zooplankton was estimated to exceed carbon fixation by a factor of 1.7 in the northern basin, possibly a result of the discharge of riverine organic carbon. Diversity and biomass of both fish and benthic fauna were lower in the Bothnian Bay, with benthic meiofauna being of relatively greater importance than macrofauna in this basin.
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| 16. |
- Langenheder, Silke, et al.
(författare)
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Growth dynamics within bacterial communities in riverine and estuarine batch cultures
- 2004
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 37, s. 137-148
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated temporal changes in community composition of bacteria growing on riverine dissolved organic carbon. Batch cultures were adjusted to riverine or estuarine salinity levels and inoculated with bacteria from these 2 environments to test whether growth patterns of bacterial taxa are influenced by salinity and/or the source of the inoculum. Changes in bacterial community composition at different stages of the growth phase were studied by 16S rDNA denaturing gradient gel electrophoresis (DGGE). Furthermore, the growth dynamics of 7 bacteria previously isolated from the estuary were followed by quantitative DNA-DNA hybridization. Growth dynamics within bacterial communities were significantly influenced by the source of the inoculum but not by salinity, suggesting that slight changes in salinity, to which riverine bacteria are exposed when discharged into the Northern Baltic Sea, are not a major regulating factor of community dynamics. Additionally, our results indicated only minor differences in the appearance and growth of bacteria when examined by quantitative DNA-DNA hybridization, whereas DGGE banding patterns suggested that there were fast- and slow-growing types of bacteria.
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| 17. |
- Langenheder, Silke, et al.
(författare)
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Salinity as a structuring factor for the composition and performance of bacterioplankton degrading riverine DOC
- 2003
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Ingår i: FEMS Microbiology Ecology. - 0168-6496 .- 1574-6941. ; 45:2, s. 189-202
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Tidskriftsartikel (refereegranskat)abstract
- The impact of salinity on the composition and functional performance (biomass production, growth efficiency and growth rates) of bacterial communities was investigated using batch cultures growing on dissolved organic carbon from a river draining into the Northern Baltic Sea. The cultures were adjusted to riverine or estuarine salinity levels and inoculated with bacteria from these two environments. Bacterial growth efficiencies differed in response to salinity and the origin of the inoculum. When salinity was adjusted to correspond to the salinity at the site where the inoculum was retrieved, growth efficiency was relatively high (11.5 +/- 2.6%). However, when bacteria were confronted with a shift in salinity, growth efficiency was lower (7.5 +/- 2.0%) and more of the utilized carbon was respired. In contrast, growth rates were higher when bacteria were exposed to a change in salinity. The composition of the bacterial communities developing in the batch cultures differed, as shown by 16S rDNA DGGE, depending on the origin of the inoculum and salinity. Reverse and direct DNA-DNA hybridization revealed salinity optima in the growth of specific bacterial strains as well as broader phylogenetic groups. Strains belonging to the alpha- and beta-Proteobacteria, Actinobacteria and gamma-Proteobacteria other than the genus Pseudomonas showed higher relative abundance under freshwater conditions, whereas strains of the genus Pseudomonas and the Cytophaga-Flavobacterium-Bacteroides group were favored by estuarine conditions. Generally, our results demonstrate functional changes associated with changes in community composition. We suggest that even moderate changes in salinity affect bacterial community composition, which subsequently leads to altered growth characteristics. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
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| 18. |
- Larsson, Ulf, et al.
(författare)
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Växtplanktonproduktion : mätningar med problem
- 2010
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Ingår i: Havet. - Stockholm : Naturvårdsverket och Havsmiljöinstitutet. - 9789162012816 ; , s. 26-29
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 19. |
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| 20. |
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| 21. |
- Muelbert, Jose H., et al.
(författare)
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ILTER : The International Long-Term Ecological Research Network as a Platform for Global Coastal and Ocean Observation
- 2019
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Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 6
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Forskningsöversikt (refereegranskat)abstract
- Understanding the threats to global biodiversity and ecosystem services posed by human impacts on coastal and marine environments requires the establishment and maintenance of ecological observatories that integrate the biological, physical, geological, and biogeochemical aspects of ecosystems. This is crucial to provide scientists and stakeholders with the support and knowledge necessary to quantify environmental change and its impact on the sustainable use of the seas and coasts. In this paper, we explore the potential for the coastal and marine components of the International Long-Term Ecological Research Network (ILTER) to fill this need for integrated global observation, and highlight how ecological observations are necessary to address the challenges posed by climate change and evolving human needs and stressors within the coastal zone. The ILTER is a global network encompassing 44 countries and 700 research sites in a variety of ecosystems across the planet, more than 100 of which are located in coastal and marine environments (ILTER-CMS). While most of the ILTER-CMS were established after the year 2000, in some cases they date back to the early 1900s. At ILTER sites, a broad variety of abiotic and biotic variables are measured, which may feed into other global initiatives. The ILTER community has produced tools to harmonize and compare measurements and methods, allowing for data integration workflows and analyses between and within individual ILTER sites. After a brief historical overview of ILTER, with emphasis on the marine component, we analyze the potential contribution of the ILTER-CMS to global coastal and ocean observation, adopting the "Strength, Weakness, Opportunity and Threats (SWOT)" approach. We also identify ways in which the in situ parameters collected at ILTER sites currently fit within the Essential Ocean Variables framework (as proposed by the Framework for Ocean Observation recommendations) and provide insights on the use of new technology in long-term studies. Final recommendations point at the need to further develop observational activities at LTER sites and improve coordination among them and with external related initiatives in order to maximize their exploitation and address present and future challenges in ocean observations.
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| 22. |
- Nilsson, Jonas, et al.
(författare)
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Havsmiljöns tillstånd : ur ett miljömåls perspektiv
- 2011
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Ingår i: Havet 2011. - Göteborg ; Stockholm : Havs-och vattenmyndigheten, Naturvårdsverket och Havsmiljöinstitutet. - 9789162012885 - 9789163397639 - 9789187025006 ; , s. 6-12
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 23. |
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| 24. |
- Nydahl, Anna, 1981-, et al.
(författare)
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Increased microbial activity in a warmer and wetter climate enhances the risk of coastal hypoxia
- 2013
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Ingår i: FEMS Microbiology Ecology. - Hoboken : Wiley-Blackwell. - 0168-6496 .- 1574-6941. ; 85:2, s. 338-347
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Tidskriftsartikel (refereegranskat)abstract
- The coastal zone is the most productive area of the marine environment and the area that is most exposed to environmental drivers associated with human pressures in a watershed. In dark bottle incubation experiments, we investigated the short-term interactive effects of changes in salinity, temperature and riverine dissolved organic matter (rDOM) on microbial respiration, growth and abundance in an estuarine community. An interaction effect was found for bacterial growth, where the assimilation of rDOM increased at higher salinities. A 3 °C rise in the temperature had a positive effect on microbial respiration. A higher concentration of DOM consistently enhanced respiration and bacterial abundance, while an increase in temperature reduced bacterial abundance. The latter result was most likely caused by a positive interaction effect of temperature, salinity and rDOM on the abundance of bacterivorous flagellates. Elevated temperature and precipitation, causing increased discharges of rDOM and an associated lowered salinity, will therefore primarily promote bacterial respiration, growth and bacterivore abundance. Our results suggest a positive net outcome for microbial activity under the projected climate change, driven by different, partially interacting environmental factors. Thus, hypoxia in coastal zones may increase due to enhanced respiration caused by higher temperatures and rDOM discharge acting synergistically.
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| 25. |
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| 26. |
- Panigrahi, Satya, et al.
(författare)
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Strong seasonal effect of moderate experimental warming on plankton respiration in a temperate estuarine plankton community
- 2013
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Ingår i: Estuarine, Coastal and Shelf Science. - : Academia Press. - 0272-7714 .- 1096-0015. ; 136, s. 269-279
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change projections forecast a 1.1-6.4 °C global increase in surface water temperature and a 3 °C increase for the Baltic Sea. This study examined the short-term interactive effects of a realistic future temperature increase (3 °C) on pelagic respiration and bacterioplankton growth and phytoplanktonphotosynthesis in situ. This study was undertaken throughout a full seasonal cycle in the northern Baltic Sea. We found marked positive short-term effects of temperature on plankton respiration but no significant effect on bacterioplankton growth or phytoplankton photosynthesis. Absolute respiration rates remained similar to other comparable environments at the in situ temperature. With the 3 °C temperature increase, respiration rates in situ increased up to 5-fold during the winter and 2-fold during the summer. A maximum seasonal Q10 value of 332 was observed for respiration during the cold winter months (twater z 0 C), and summer Q10 values were comparatively high (9.1). Q10 values exhibited a significant inverse relationship to water temperature during winter. Our results thereby suggest that plankton respiration in this coastal zone is more temperature sensitive than previously reported. In addition, field data indicated that plankton respiration switched from being temperature limited to being limited by dissolved organic carbon (DOC) after the simulated temperature increase. Assuming that our observations are relevant over longer time scales, climate change may worsen hypoxia, increase CO2 emissions and create a more heterotrophic food web in coastal zones with a high load of riverine DOC.
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| 27. |
- Panigrahi, Satya, et al.
(författare)
-
Variability of nutrients and phytoplankton biomass in a shallow brackish water ecosystem : (Chilika Lagoon, India)
- 2009
-
Ingår i: Limnology. - : Springer Science and Business Media LLC. - 1439-8621 .- 1439-863X. ; 10:2, s. 73-85
-
Tidskriftsartikel (refereegranskat)abstract
- Seasonal and spatial variations in water quality parameters, such as nutrients [NH4 (+)-N, NO (2) (-) -N, NO (3) (-) -N, PO (4) (3-) -P, total nitrogen (TN) and total phosphorus (TP)], Secchi disc depth, salinity, dissolved oxygen, chlorophyll a, primary productivity and phytoplankton standing stock, were studied in Chilika Lagoon (from 27 sampling locations) during 2001-2003 to assess the present ecological status. The study was undertaken after a major hydrological intervention in September 2000, which connected the lagoon body and the Bay of Bengal via a manmade opening (new mouth). Current and old data on water quality were also compared to establish the changes that had occurred after the hydrological intervention. Multivariate techniques and gridding methods were used to investigate the spatial and seasonal variability of the data and to characterize the trophic evolution of the basin. Results of principal component analysis (PCA) indicated that the 27 stations can be classified into five groups based on similarities in the temporal variation of nutrients, chlorophyll a concentration, salinity, and other physicochemical parameters. The tributaries and the exchange of lagoon water with the Bay of Bengal most probably determine the water quality and the dynamics of the ecosystem. Hydrodynamics of the lagoon, weed coverage, input of urban sewage through tributaries and agricultural runoff are probably the key factors controlling the trophic conditions of the lagoon. An increase in salinity and total phosphorus was noted after the new mouth was opened, while the total suspended sediment load, the water column depth, and nitrogenous nutrients decreased. The new mouth opening also brought changes in the phytoplankton species composition.
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| 28. |
- Ramnefält, Richard, et al.
(författare)
-
Plan for centralized data portal for mesocosm
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A centralized international data tool for primary experimental data is developed to achieve Open science with Open data. This will promote meta-analyses across environments and times. A prerequisite is harmonized data entry, with a reliable quality. Simultaneously, the primary data shell shall provide support for individual research groups by easy entering of primary data, integrated quality assurance tools, including open data archiving, facilitating evaluation, and reporting of research data. Time for data administration should be minimized and scientific work optimized.The demands and expectations of the primary data shell have been collected by three workshops and a questionnaire. We use the term “shell” to reflect its implementation as a layer filtering primary data prior to archiving in an existing EU-data base for research data.By adopting an interactive and inclusive (i.e. agile) approach this plan will be an organic document, evolving by multiple iterations between research groups and developers. In the first steps of the development, the model of the computer components required was defined and a sketch created, defining its key parts. The user interface will evolve in iterations in later stages of the development process.The aim is to create a user-friendly, versatile and logical data tool. Trust in the primary data shell from the end users is crucial for a successful implementation. Users should feel that they have control over and access to their own data, safe archiving with reliable back-up routines lowering barriers for data sharing. We also use a generic approach enabling easy administration of common experimental research data from any subject field.
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| 29. |
- Ramnefält, Richard, et al.
(författare)
-
Report of centralised data portal launch
- 2022
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A pilot version of a web interface primary data shell has been developed. The shell was pre-tested by a selected group of dedicated partners, improved and launched for testing by partners in the whole AQUACOSM-plus community. By a couple of introductory meetings, partners were shown the procedure to enter a mesocosm experiment and add primary data. Partners had the opportunity to test the platform for 2,5 months and give feed-back with suggestions of improvements. Suggestions for improvements were noted from the partners and additional improvements were furthermore identified by the task group itself. No major requirements of changes of the basic structure of the primary data shell were requested. Most suggested improvements for the six prioritized variables are planned to be remedied within the project period. The need of resources to develop a fully operational shell will be presented in the final report from this task.
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| 30. |
- Rogers, Stuart, et al.
(författare)
-
Marine strategy framework directive : Task Group 4 report : food webs
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Marine Strategy Framework Directive (2008/56/EC) (MSFD) requires that the European Commis-sion (by 15 July 2010) should lay down criteria and methodological standards to allow consistency in approach in evaluating the extent to which Good Environmental Status (GES) is being achieved. ICES and JRC were contracted to provide scientific support for the Commission in meeting this obligation.A total of 10 reports have been prepared relating to the descriptors of GES listed in Annex I of the Directive. Eight reports have been prepared by groups of independent experts coordinated by JRC and ICES in response to this contract. In addition, reports for two descriptors (Contaminants in fish and other seafood and Marine Litter) were written by expert groups coordinated by DG SANCO and IFREMER respectively.A Task Group was established for each of the qualitative Descriptors. Each Task Group consisted of selected experts providing experience related to the four marine regions (the Baltic Sea, the North-east Atlantic, the Mediterranean Sea and the Black Sea) and an appropriate scope of relevant scientif-ic expertise. Observers from the Regional Seas Conventions were also invited to each Task Group to help ensure the inclusion of relevant work by those Conventions. This is the report of Task Group 4 Food webs.
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| 31. |
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| 32. |
- SHELDON, RW, et al.
(författare)
-
NANOPLANKTON AND PICOPLANKTON GROWTH AND PRODUCTION IN THE BAY OF VILLEFRANCHE-SUR-MER (NW MEDITERRANEAN)
- 1992
-
Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 241:2, s. 91-106
-
Tidskriftsartikel (refereegranskat)abstract
- Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 mum) flagellates but towards the end it was more or less equally divided between the nano- and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nano- or picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.
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| 33. |
- Vass, Máté, et al.
(författare)
-
Co-occurrences enhance our understanding of aquatic fungal metacommunity assembly and reveal potential host–parasite interactions
- 2022
-
Ingår i: FEMS Microbiology Ecology. - : Oxford University Press. - 0168-6496 .- 1574-6941. ; 98:11
-
Tidskriftsartikel (refereegranskat)abstract
- Our knowledge of aquatic fungal communities, their assembly, distributions and ecological roles in marine ecosystems is scarce. Hence, we aimed to investigate fungal metacommunities of coastal habitats in a subarctic zone (northern Baltic Sea, Sweden). Using a novel joint species distribution model and network approach, we quantified the importance of biotic associations contributing to the assembly of mycoplankton, further, detected potential biotic interactions between fungi–algae pairs, respectively. Our long-read metabarcoding approach identified 493 fungal taxa, of which a dominant fraction (44.4%) was assigned as early-diverging fungi (i.e. Cryptomycota and Chytridiomycota). Alpha diversity of mycoplankton declined and community compositions changed along inlet–bay–offshore transects. The distributions of most fungi were rather influenced by environmental factors than by spatial drivers, and the influence of biotic associations was pronounced when environmental filtering was weak. We found great number of co-occurrences (120) among the dominant fungal groups, and the 25 associations between fungal and algal OTUs suggested potential host–parasite and/or saprotroph links, supporting a Cryptomycota-based mycoloop pathway. We emphasize that the contribution of biotic associations to mycoplankton assembly are important to consider in future studies as it helps to improve predictions of species distributions in aquatic ecosystems.
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| 34. |
- Vass, Mate, et al.
(författare)
-
Microeukaryote community coalescence strengthens community stability and elevates diversity
- 2024
-
Ingår i: FEMS Microbiology Ecology. - : Oxford University Press. - 0168-6496 .- 1574-6941. ; 100:8
-
Tidskriftsartikel (refereegranskat)abstract
- Mixing of entire microbial communities represents a frequent, yet understudied phenomenon. Here, we mimicked estuarine condition in a microcosm experiment by mixing a freshwater river community with a brackish sea community and assessed the effects of both environmental and community coalescences induced by varying mixing processes on microeukaryotic communities. Signs of shifted community composition of coalesced communities towards the sea parent community suggest asymmetrical community coalescence outcome, which, in addition, was generally less impacted by environmental coalescence. Community stability, inferred from community cohesion, differed among river and sea parent communities, and increased following coalescence treatments. Generally, community coalescence increased alpha diversity and promoted competition from the introduction (or emergence) of additional (or rare) species. These competitive interactions in turn had community stabilizing effect as evidenced by the increased proportion of negative cohesion. The fate of microeukaryotes was influenced by mixing ratios and frequencies (i.e. one-time versus repeated coalescence). Namely, diatoms were negatively impacted by coalescence, while fungi, ciliates, and cercozoans were promoted to varying extents, depending on the mixing ratios of the parent communities. Our study suggests that the predictability of coalescence outcomes was greater when the sea parent community dominated the final community, and this predictability was further enhanced when communities collided repeatedly.
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| 35. |
- Verma, Ashish, et al.
(författare)
-
Prokaryotic maintenance respiration and growth efficiency field patterns reproduced by temperature and nutrient control at mesocosm scale
- 2023
-
Ingår i: Environmental Microbiology. - : John Wiley & Sons. - 1462-2912 .- 1462-2920. ; 25:3, s. 721-737
-
Tidskriftsartikel (refereegranskat)abstract
- The distribution of prokaryotic metabolism between maintenance and growth activities has a profound impact on the transformation of carbon substrates to either biomass or CO2. Knowledge of key factors influencing prokaryotic maintenance respiration is, however, highly limited. This mesocosm study validated the significance of prokaryotic maintenance respiration by mimicking temperature and nutrients within levels representative of winter and summer conditions. A global range of growth efficiencies (0.05-0.57) and specific growth rates (0.06-2.7 d(-1)) were obtained. The field pattern of cell-specific respiration versus specific growth rate and the global relationship between growth efficiency and growth rate were reproduced. Maintenance respiration accounted for 75% and 15% of prokaryotic respiration corresponding to winter and summer conditions, respectively. Temperature and nutrients showed independent positive effects for all prokaryotic variables except abundance and cell-specific respiration. All treatments resulted in different taxonomic diversity, with specific populations of amplicon sequence variants associated with either maintenance or growth conditions. These results validate a significant relationship between specific growth and respiration rate under productive conditions and show that elevated prokaryotic maintenance respiration can occur under cold and oligotrophic conditions. The experimental design provides a tool for further study of prokaryotic energy metabolism under realistic conditions at the mesocosm scale.
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| 36. |
- Verma, Ashish, et al.
(författare)
-
Prokaryotic variables from a indoor-mesocosm experiment measured during the winter in the Northern Bothnian Sea
- 2023
-
Annan publikationabstract
- The primary data was collected during the indoor-mesocosm experiment conducted in March 2020 at Umea Marine Science Centre, Umea University, Sweden situated in the Northern Bothnian Sea (63° 34ˈN, 19° 50ˈE). A full factorial experiment was set with temperature and the addition of nutrients as treatment factors with a natural pelagic food web containing all trophic levels except fish. A total of four experimental treatments were set up with three replicates each: C, control (1°C, no additions); N (1°C,+ nutrients); T (10°C, no additions) and TN (10°C, + nutrients). For each treatment, eight different samplings were done in triplicates. The variables in the data include the prokaryotic abundance (PA), growth (PG), respiration (PR), specific prokaryotic respiration (ρ), specific growth rates (µ), growth efficiency (PGE), dissolved organic carbon (DOC), total dissolved phosphorus (TDP) and total dissolved nitrogen (TDN).
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| 37. |
- Viitasalo, Markku, et al.
(författare)
-
Environmental Impacts—Marine Ecosystems
- 2015
-
Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - London : Springer. - 9783319160061 - 9783319160054 ; , s. 363-380
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Increase in sea surface temperature is projected to change seasonal succession and induce dominance shifts in phytoplankton in spring and promote the growth of cyanobacteria in summer. In general, climate change is projected to worsen oxygen conditions and eutrophication in the Baltic Proper and the Gulf of Finland. In the Gulf of Bothnia, the increasing freshwater discharge may increase the amount of dissolved organic carbon (DOC) in the water and hence reduce phytoplankton productivity. In winter, reduced duration and spatial extent of sea ice will cause habitat loss for ice-dwelling organisms and probably induce changes in nutrient dynamics within and under the sea ice. The projected salinity decline will probably affect the functional diversity of the benthic communities and induce geographical shifts in the distribution limits of key species such as bladder wrack and blue mussel. In the pelagic ecosystem, the decrease in salinity together with poor oxygen conditions in the deep basins will negatively influence the main Baltic Sea piscivore, cod. This has been suggested to cause cascading effects on clupeids and zooplankton.
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| 38. |
- Vikström, Kevin, 1988-, et al.
(författare)
-
Havets dolda andetag
- 2019
-
Ingår i: Havsutsikt. - : Havsmiljöinstitutet. - 1104-0513 .- 2002-858X. ; :2, s. 6-8
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Det råder syrebrist i haven. Stora pengar pumpas årligen in i åtgärder mot övergödning, i hopp om att lägre tillväxt av alger och växtplankton ska leda till att syrehalterna går upp igen. Men vår forskning visar att havssamhället inte slutar andas bara för att det växer långsammare. Snarare tvärtom.
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| 39. |
- Vikström, Kevin, et al.
(författare)
-
High influence of baseline respiration in a sub-Arctic coastal ecosystem
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Respiration is a key metabolic process in the marine environment that is usually assumed to be driven by phytoplankton production. However, respiration in the absence of contemporary phytoplankton production, termed baseline respiration, can influence the energetics of an ecosystem and its sensitivity to hypoxia. Direct studies of baseline respiration and its importance for coastal oxygen status are currently lacking. This study aims to obtain a first estimate of baseline respiration in a sub-arctic estuary, determine its contribution to annual plankton community respiration and identify the main carbon sources. The four different methods used to define baseline respiration converged on an average rate of 4.2 mmol O2 m-3 d-1 ± 0.1 (SE), corresponding to an annual contribution of 50 % of planktonic respiration on the basin scale. Respiration during the winter season (sporadic ice cover) was significant and comprised 25 % of annual pelagic respiration. No correlation between plankton respiration and phytoplankton production occurred on the intra-annual scale, while there was a weak exponential dependence on riverine total organic carbon inflow combined with phytoplankton production (i.e., major C input). Measured carbon sources could supply most (78 %) of the annual plankton respiration but only 39 % of the winter season respiration, suggesting some missing carbon sources. Nitrification had a negligible (≤ 2.4 %) effect on baseline respiration in the system. The results showed that baseline respiration could constitute a significant share of coastal plankton respiration, when allochthonous carbon sources dominate the carbon supply.
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| 40. |
- Vikström, Kevin, 1988-
(författare)
-
Importance of bacterial maintenance respiration and baseline respiration for development of coastal hypoxia
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reduced oxygen concentrations and increasing hypoxic zones havebecome more common in the sea due to climate change andeutrophication. The main cause of oxygen loss in oxygenatedenvironments is respiration. Respiration rates can be estimated usingoptode methodologies which utilize dynamic luminescence quenching toestimate the oxygen concentration declines in dark incubations. Apublished optode methodology was improved by using optodes withtitanium housing instead of plastic housing plausibly trapping oxygen.Drift was highly reduced by the titanium casings leading to a higherprecision and lower detection limit of 0.97 mmol O2 m-3 d-1. 28% ofmeasurements were shown to have non-linear oxygen concentrationdeclines. The rate of oxygen change was derived with a 2nd degreepolynomial at 1 hour from the incubation start. The majority of non-lineardeclines were concave and due to carbon substrate limitation. Analyzingnon-linear trends linearly, a common practice, leads to anunderestimation of respiration by up to 64%.Bacterial maintenance respiration (Rm) was studied using anecophysiological model unverified in natural environments. The modelwas applicable at high productivities but a quadratic model wasdemonstrated to give a better fit. Rm was found to represent a significantpart in the sub-arctic estuary contributing to 58% of the annual specificbacterial respiration. Therefore, Rm may be more important in nature thanpreviously recognized. The ecophysiological model is driven solely by thebacterial specific growth rate (μ) where the relative influence of Rm iselevated as μ decreases. As a consequence, I hypothesize that a reductionin nutrients may not decrease the oxygen consumption but rather shiftbacterial growth based respiration to Rm as μ approaches zero.Baseline respiration (Rbl), defined as ecosystem respiration disconnectedfrom contemporary primary produced carbon, was also studied. Rbl wasshown to be largely supplied by allochthonous carbon in a coastalecosystem and had a contribution of 50% to the annual planktoncommunity respiration in the sub-arctic estuary studied. I claim that Rbland Rm are crucial to include for understanding and managingdevelopment of aquatic hypoxia in an effective and economic manner.
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| 41. |
- Vikström, Kevin, et al.
(författare)
-
Importance of Bacterial Maintenance Respiration in a Subarctic Estuary : a Proof of Concept from the Field
- 2019
-
Ingår i: Microbial Ecology. - : Springer. - 0095-3628 .- 1432-184X. ; 77:3, s. 574-586
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial respiration contributes to atmospheric carbon dioxide accumulation and development of hypoxia and is a critical, often overlooked, component of ecosystem function. This study investigates the concept that maintenance respiration is a significant proportion of bacterial respiration at natural nutrient levels in the field, advancing our understanding of bacterial living conditions and energy strategies. Two river-sea transects of respiration and specific growth rates were analyzed representing low- and highproductivity conditions (by in situ bacterial biomass production) in a subarctic estuary, using an established ecophysiological linear model (the Pirt model) estimating maintenance respiration. The Pirt model was applicable to field conditions during high, but not low, bacterial biomass production. However, a quadratic model provided a better fit to observed data, accounting for the maintained respiration at low μ. A first estimate of maintenance respiration was 0.58 fmol O2 day−1 cell−1 by the quadratic model. Twenty percent to nearly all of the bacterial respiration was due to maintenance respiration over the observed range of μ (0.21– 0.002 day−1 ). In the less productive condition, bacterial specific respiration was high and without dependence on μ, suggesting enhanced bacterial energy expenditure during starvation. Annual maintenance respiration accounted for 58% of the total bacterioplankton respiration based on μ from monitoring data. Phosphorus availability occasionally, but inconsistently, explained some of the remaining variation in bacterial specific respiration. Bacterial maintenance respiration can constitute a large share of pelagic respiration and merit further study to understand bacterial energetics and oxygen dynamics in the aquatic environment.
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| 42. |
- Vikström, Kevin, et al.
(författare)
-
Improved accuracy of optode-based oxygen consumption measurements by removal of system drift and nonlinear derivation
- 2019
-
Ingår i: Limnology and Oceanography-Methods. - : Wiley. - 1541-5856. ; 17:3, s. 179-189
-
Tidskriftsartikel (refereegranskat)abstract
- This method evaluation aimed to improve the accuracy and precision of the previously published method to measure oxygen consumption using optodes with integrated temperature and salinity correction in dark incubations. Significant short-term system drift currently requires a correction to remove the drift, thus reducing the precision of the oxygen consumption rates. Frequent nonlinear declines in oxygen concentration with time also call for improved data analysis and identification of its origin. Optodes in titanium casings (Aanderaa (TM) model 4330) with low oxygen binding properties showed no significant system drift in autoclaved seawater. Nonlinear oxygen dynamics fitting a quadratic polynomial occurred in 28% of 230 field samples, independent of season and water depth. Polynomial curve fit resulted in 64% higher respiration rates when derived within 1 h of the quality assured incubation, than obtained when using linear fit. Carbon substrate limitation explained the nonlinearity of oxygen decline during dark incubations. Pretreatment of the optode attached to stoppers with 0.3 mol dm(-3) hydrochloric acid resulted in the most stable performance of the sensor and simultaneously provided proper cleaning of the equipment. A conservative detection limit of 0.97 mu mol O-2 dm(-3) d(-1) was calculated for the titanium optodes, matching other methods for oxygen consumption reported in the literature. Thus, we recommend the use of model 4330 optode pretreated with HCl and the derivation of initial respiration rates by a quadratic polynomial function for best accuracy and precision of oxygen consumption in oxygenated surface waters.
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| 43. |
- Vikström, Kevin, 1988-, et al.
(författare)
-
Strong Influence of Baseline Respiration in an Oligotrophic Coastal Ecosystem
- 2020
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Respiration is a key metabolic process in the marine environment and contemporary phytoplankton production (PhP) is commonly assumed the main driver. However, respiration in the absence of contemporary PhP, termed baseline respiration, can influence the energetics of an ecosystem and its sensitivity to hypoxia. Direct studies of baseline respiration are currently lacking. This study aims to obtain a first estimate of baseline respiration in a sub-arctic estuary and determine its contribution to plankton community respiration. Three approaches used to define baseline respiration determined the average rate to be 4.1 ± 0.1 (SE) mmol O2 m–3 d–1. A hypsographic model at the basin scale accounting for seasonal variation estimated an annual contribution of 30% baseline respiration to planktonic respiration. There was no correlation between plankton respiration and PhP, but a significant linear dependence was found with the total carbon supply from phytoplankton and riverine input. The sum of dissolved organic carbon transported by rivers, provided by both benthic and pelagic algae, could sustain 69% of the annual plankton respiration, of which as much as 25% occurred during winter. However, only 32% of the winter season respiration was explained, indicating that unknown carbon sources exist during the winter. Nitrification had a negligible (≤2.4%) effect on baseline respiration in the system. The results show that baseline respiration accounted for a significant percentage of coastal plankton respiration when allochthonous sources dominated the carbon supply, weakening the respiration-to- PhP relationship.
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| 44. |
- Wikner, Johan, 1961-, et al.
(författare)
-
Annual Study of Bacterioplankton Community Dynamics.
- 1991
-
Ingår i: Limnology and Oceanography. - : American Society of Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 36:7, s. 1313-1324
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial growth, abundance, and grazing were measured simultaneously during a full seasonal cycle in a temperate brackish water estuary, covering diel and seasonal variability. Growth of bacteria was balanced by bacterivory on an annual basis, and observed net change in bacterial numbers matched the net change calculated by a simple Lotka-Volterra equation lacking immigration or emigration terms. Bacterial growth was dependent on water temperature below 6-degrees-C, but other factors dominated at higher temperatures. The community clearance rate of the bacterivores was stringently regulated at 0.6 d-1, showing a linear functional response within the range of natural bacterial abundances recorded. Furthermore, bacterivores showed a threshold at 7 x 10(5) bacteria ml-1 when grazing ceased, suggesting that pelagic bacteria have a numerical refuge promoting coexistence with bacterivores in aquatic environments. The observed lack of timing between bacterial growth and grazing in spring allowed accumulation of bacterial cells, but grazing exceeded growth in winter. We inferred that the specific growth rate of the bacterial community and the community clearance rate of bacterivores together determined change in and abundance of bacterioplankton in the waters examined.
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| 45. |
- Wikner, Johan, 1961-, et al.
(författare)
-
Bacterioplankton intra-annual variability: importance of hydrography and competition
- 1999
-
Ingår i: Aquatic Microbial Ecology. - Oldendorf : Inter-Research. - 0948-3055 .- 1616-1564. ; 20:3, s. 245-260
-
Tidskriftsartikel (refereegranskat)abstract
- Field data from a 1.5 yr intensive study of 1 coastal (0 to 20 m) and 2 offshore stations (0 to 100 m) in the northern Baltic were analysed. Specific interest was paid to the difference in the spatiotemporal variation of bacterioplankton and its controlling factors. Less than 31% of the annual bacterial biomass production (P-b) occurred in the photic zone during the productive season at the offshore stations. This suggested an uncoupling between P-b and phytoplankton carbon fixation, which was further supported by the lack of a significant correlation between these variables in the photic zone. The basin with high allochthonous loading and long residence time showed high P-b relative to autochthonous carbon fixation and low variance of P-b and bacterial abundance (N-b), suggesting an important contribution of terrestrial dissolved organic carbon to the carbon and energy supply. Bacterial per capita growth rate (r(c)) was highest during spring, while P-b was highest during summer at all stations. The seasonal variation in P-b was mainly explained by variation in the r(c), rather than in N-b. A positive correlation of N-b with temperature. and a negative correlation with salinity, suggested that >61% of the seasonal variation in N-b was a consequence of the formation of a stratified photic zone with a higher carrying capacity. Temperature limitation of r(c) only occurred in the stratified photic zone, suggesting that other growth factors were sufficient during this period. A density limitation of the maximum r(c) was observed at all stations during autumn and winter in both depth layers, suggesting competition to be of periodic importance. Bacterioplankton with a low r (intrinsic growth rate) and high K (carrying capacity) strategy dominated when sedimenting particles were a major resource in the aphotic zone, while the opposite strategy dominated during winter at low cell densities, when dissolved substrates were the major resource.
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| 46. |
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| 47. |
- Wikner, Johan, 1961-, et al.
(författare)
-
Coastal filter effect by microbial mineralization of riverine DOC in a sub-arctic river-estuary gradient
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The existence of a coastal filtering effect was studied in a 16 km boreal river-estuary system (RES) during contrasting low and high production conditions. Marked transformations occurred within 5 km (salinity 3) from the river mouth for many of the variables during high productive conditions. During the less productive season changes were small and occurred closer to the river mouth. Active transformation dominated the patterns detected in August (53 %), while mixing of river and coastal marine water was the dominant process in April. Bacterial community respiration was similar during both seasons averaging 2.6 μmol O2 dm-3 d-1, indicating efficient remineralization of riverine dissolved organic carbon (DOC). This was further reflected in a low and variable bacterial growth efficiency (BGE) with a mean of 12 % in the surface water at high productivity, but only 3 % at low productivity conditions. Bacterial community growth (BCG) showed strong relationship to water temperature at both seasons indicating energy limitation. Some indication of removal of nitrogen was observed, while no removal of phosphorus could be demonstrated. Phosphorus concentration showed a strong reciprocal power-function relationship to BCG, suggesting efficient assimilation of the limiting nutrient at carbon sufficiency. Marked spatial changes in diversity of phytoplankton, protozoa and bacterioplankton occurred at low salinities within 1 km from the river mouth. We conclude that this subarctic estuary acts as a coastal filter mainly by remineralizing riverine DOC to CO2.
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| 48. |
- Wikner, Johan, 1961-, et al.
(författare)
-
Differences in consumption of allochthonous DOC under limnic and estuarine conditions in a watershed
- 1999
-
Ingår i: Aquatic Microbial Ecology. - Oldendorf : Inter-Research. - 0948-3055 .- 1616-1564. ; 17:3, s. 289-299
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Tidskriftsartikel (refereegranskat)abstract
- A temporal study of the bacterial utilisation of allochthonous dissolved organic carbon (DOC) was performed in a lake and estuary situated in the same boreal watershed. A greater utilisation of allochthonous DOC was observed under estuarine as compared to Limnic conditions. However, the bacterial biomass yield was not significantly different between the environments, indicating a lower growth efficiency on allochthonous DOC by the estuarine bacterioplankton. The largest fraction of the allochthonous DOC utilised (20 %) was observed under estuarine conditions and coincided with the spring flood. The utilisation of allochthonous DOC and bacterial biomass yield in the experimental bottles was Limited by the availability of nitrogen or phosphorus in both environments. Our results showed that the major bacterial transformation of DOC occurred in the estuarine rather than the Limnic environment, due to the shift in physicochemical milieu and bacterial assemblage. However, the estuarine bacteria also respired a greater fraction of the DOC utilised than their limnic counterparts.
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| 49. |
- Wikner, Johan, 1961-, et al.
(författare)
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Evidence for a tightly coupled nanoplanktonic predator-prey link regulating the bacterivores in the marine-environment
- 1988
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Ingår i: Marine Ecology Progress Series. - Oldenburg : Inter-Research. - 0171-8630 .- 1616-1599. ; 50:1-2, s. 137-145
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Tidskriftsartikel (refereegranskat)abstract
- A coupled predator-prey chain, starting with bactenvores, was invest~gated using the mlnicell recapture technique (MiniCap) Water samples were subjected to slze fract~onation wth decreasing filter pore sue in order to obtain a successive truncation of the microbial food chaln Our results showed that the malor bacterivores were flagellates in the size range of 1 to 3 pm The truncation of the food chain caused increased or decreased predation on the bactena, d e p e n d~n go n whether the bacterivores 'ivere released from or subjected to increased predat~on pressure We present a model describing trophic interactions between organisms less than 12 pm In size This model suggests 4 trophic levels to form a regulatory chain exer t~nga tight control on major bacterivores.
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| 50. |
- Wikner, Johan, Professor, 1961-, et al.
(författare)
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Extensive prokaryotic maintenance respiration in the sea influenced by osmoregulation
- 2023
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Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Microbial respiration is the major process consuming oxygen in the biosphere. The relative energy demand from growth of biomass or maintenance activities determines the regulation of respiration with impact on how the development of hypoxia and CO2 emissions is controlled. This coupling is crucial for understanding the life history and associated ecological interactions of microorganisms. However, the knowledge of rate and regulating factors of maintenance respiration in the biosphere is limited. In this study, we demonstrated significant relationships in marine field samples where the prokaryotic specific growth rate predicts cell-specific respiration, in accordance with theory from culture models, over a 10-fold salinity range. This enables the first reported direct estimates of maintenance respiration in nature to show a 6-fold variation between 0.12-0.62 fmol O2 cell-1 d-1, comprising 29-72% of prokaryotic specific respiration. The lowest maintenance respiration occurred at salinity close to physiological osmolarity, suggesting osmoregulation as one of the more energy-consuming maintenance activities. A conservative global estimate of maintenance respiration accounted for 66% of the total prokaryotic respiration in the ocean´s mixed layer. This means that maintenance activities dominate the use of the energy generated by prokaryotic respiration in the sea, where osmoregulation is one significant energy consumer. Consequently, maintenance respiration and its regulation must be included in ecological and biogeochemical models to accurately project and manage the development of hypoxia and CO2 emissions from the ocean.
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